Human nutrition is based on the good balance of the foods consumed. The entire range of essential nutrients is available in almost anything that we eat, be it a fruit or vegetable, meat or milk or eggs, fungi or algae or even insects and worms. What we prefer to eat is dependent on the range of socio-economic, behavioural and adaptive milieus in which we live. By definition, a vegetarian is one who sources foods that are primarily of plant origin. A lacto vegetarian includes milk, a lacto-ovo vegetarian includes milk and eggs, and a vegan includes neither milk nor eggs. There are also several religion-based variants of vegetarianism such as Jain vegetarianism and Buddhist vegetarianism.
Vegetarianism is an immensely debated topic and is coloured by political ideologies. Nutritionally, one could argue either way. Vegetarian foods have several advantages and so do non-vegetarian foods. Plant foods are rich in micronutrients such as vitamins and minerals and several bioactive molecules which are collectively good for health. They are anticancer, antioxidant and anti-atherogenic. The nutrition community worldwide recommends a daily intake of 400 G of fruits and vegetables to protect us from infections and cancers. Plant foods are rich in potassium and higher potassium intake will reduce the sodium load in our body and thus maintain a lower blood pressure which in turn reduces the risk of heart attacks and cerebral strokes.
Vegetarian foods are endowed with fibre, both soluble and insoluble. Soluble fibres like oligo saccharides provide the nutrition for good bacteria in our gut, which is now considered to be the key to good health. Insoluble fibre gives bulk to our meal and causes satiety or feeling of fullness, thus preventing us from overeating. It also gives the needed bulk to stools and helps in easy evacuation and prevents constipation. Since most plant foods are 60 per cent to 80 per cent made up of water, the critical fluid requirements are also taken care of.
However, there are certain disadvantages. Most vegetarian foods are poor in iron and even if present, it is less bio-available (absorbed into the body). Due to high fibre content, some micronutrients may not be fully absorbed. The quantity and quality of proteins through vegetable sources is about 65 per cent of animal sources like meat, milk or eggs.
A lacto vegetarian or a lacto ovo-vegetarian will be able to meet their protein requirements easily. A vegan would be at a disadvantage unless they take protein supplements or a high quality vegetarian protein like soya protein. Protein supplements in the market are often of animal origin and may not be acceptable to vegans or vegetarians.
A cereal-pulse combination diet like rice/wheat of about 4 portions and 1 portion of pulse will provide all the required essential amino acids, yet digestibility would be around 65 per cent when compared with meat/milk/egg protein.
Fats derived from vegetarian sources (liquid oils) are certainly a better option than those derived from animal fat, provided they are well-balanced, with all the three major groups of fatty acids saturated, monounsaturated and polyunsaturated and with sufficient amount of omega 3. Dairy fat is mainly saturated and also contains cholesterol, like animal fat. The present evidence does not provide any cardiac advantage of reduced cholesterol intakes since more than 60 per cent of the body cholesterol is produced within the body. Saturated fat from animals is a high risk for heart disease if taken in excess.
Trans-fat, that is used in bakery products and many snack foods, is from hydrogenated vegetable oils and was thought to be a good substitute for ghee, but is more harmful than saturated fat and is to be avoided.
Climate change and Vegetarianism
Global warming is attributed to the emission of greenhouse gases (eg carbon dioxide and methane) from the earth. Livestock agriculture contributes more than 15 per cent of the GHG and is a significant cause for global warming. (Gerber et al FAO 2013).
More the non-vegetarianism, the greater will be its contribution to warming. With global warming there would be severe droughts and floods that would affect the production of fodder crops which are needed for livestock maintenance. Livestock rearing and production of meat and dairy will be a challenge. The scarcity of water will make it difficult to produce meat. (See graph).
It is evident that non-veg foods need 10 to 20 times more water than veg. The only non-veg food that should be preferred is seafood, and maybe insects, since they are the species that will breed well even with global warming and water shortages. The World Health Organisation has stated that insect protein, which is a good quality protein, may be the future protein source under these circumstances.
Biotechnology and stem cell technology are coming up with alternatives in laboratory grown muscles/meat using the in vitro culturing process which is a form of cellular agriculture.
Sea food production may come down if ocean temperatures go up and inland fisheries may not be possible with acute water shortage. Fish flesh is much healthier that meat and some coastal vegetarianism includes fish as a vegetable. Fish fat is good for the heart and the brain.
It is wrong to think that vegetarianism is good for the heart or brain. In India, the major contributor to deaths due to heart attacks and for the development of diabetes is a fat in the blood called triglycerides which comes out of high carbohydrate intakes rather than fat or cholesterol. Vegetarians should ensure that they do not fill their stomachs with a lot of cereals and refined carbohydrate products made of maida and/or sugar.
In conclusion, vegetarianism is a better option in the ensuing era of adverse climate change.
Protein needs should be met through good quality proteins made by modern technology rather than dairy or meat. Most micro-nutrients are available in vegetarian foods, except for a few which can be supplemented.
Veganism is an extreme, but with careful dietary management it can be sustainable too. Non-vegetarians should minimise meat consumption and probably stay with seafood.
We need education and behavioural change to develop vegetarian preferences right from a young age.
(The author is former director, ICMR and National Institute of Nutrition, Hyderabad, and president of the Nutrition Society of India.)...